(a) Field of the Invention
The present invention relates to a method for preparing sulfones. The sulfones prepared by the method of the present invention are characterized by having bisphenyl skeletons, effectively used as materials for preparing, for instance, synthetic resins, dyes, surfactants, agricultural chemicals and medicines as well as developers for recording paper and, in particular, the synthetic resins derived from these sulfones are characterized by and excellent in high transparency, heat resistance and impact resistance.
(b) Description of the Prior Art
Methods for preparing sulfones as contemplated by the present invention are disclosed in U.K. Patent No. 1,298,822 and Polymer, 1977, 18 (April), p. 354.
In the method as disclosed in U.K. Patent No. 1,298,822, 4-nitrobiphenyl is used as a starting material and the method comprises a relatively large number of steps. For this reason, it suffers from the problem of high production cost. Further the carcinogenicity of 4-nitrobiphenyl has been talked about. Therefore, it would not always be an industrially excellent method. On the other hand, the method disclosd in Polymer, 1977, 18 (April), p. 354 utilizes carbonate of 4-hydroxybiphenyl as a starting material. However, this method likewise suffers from the problems in that the production of the carbonate is quite troublesome and that a relatively large amount of an organic solvent having a high boiling point must be used during the condensation reaction because of the relatively high melting point of the carbonate.